Numerous firearms employ cartridge magazines for storing cartridges and for successively feeding cartridges into the firing chamber of the firearm. A cartridge magazine typically includes a body defining a chamber for storing cartridges and a mechanism to facilitate successively positioning cartridges within the firing chamber of the weapon. Cartridge magazines are normally purchased empty and must be loaded with cartridges by the consumer. In use, a loaded cartridge magazine is disposed within the well of a firearm and is securely engaged to the firearm using a releasable spring locking mechanism integral to the firearm. The magazine may be removed from the firearm for storage, reloading or other purposes by releasing the spring locking mechanism.
The firearm well of a Colt 0.45 caliber pistol defines a chamber within the grip of the pistol for receiving a cartridge magazine. The well of a 0.45 caliber pistol includes a spring biasing mechanism which urges the magazine out of the well and a releasable locking mechanism integral to the pistol for securely engaging the magazine within the well against the bias provided by the spring mechanism. In use, a loaded 0.45 cartridge magazine is manually inserted into the firearm well of the pistol and securely engaged to the firearm by the releasable locking mechanism. When inserting a magazine into the well of a firearm, a user must apply a force to the base of the magazine sufficient to overcome the resistance provided by the spring biasing mechanism. The magazine may be ejected from the pistol by releasing the locking mechanism, usually accomplished by pressing a button near the trigger of the pistol. Once the locking mechanism has been released the magazine is forcibly ejected from the well by the spring biasing mechanism.
A standard 0.45 caliber magazine holds seven cartridges and is dimensioned such that the base of the magazine is substantially flush with the base of the pistol's handle when the magazine is engaged in the well of the firearm. Most 0.45 caliber magazines include a spring-driven mechanism within the magazine body for successively positioning cartridges within the firing chamber of the pistol.
In certain instances, especially in sport or competition shooting, shooters may find it advantageous to use extended capacity cartridge magazines. It is therefore desirable to provide an extended capacity cartridge magazine for use with a firearm. In this regard it is known in the art to provide extended capacity cartridge magazines which hold more than the standard seven cartridge magazine. One such extended capacity magazine is illustrated in FIGS. 1-3. FIG. 1 is an exploded assembly view of an extended capacity magazine 10 for use with a 0.45 caliber pistol having a body 12 formed from steel or other like metal and a base 20 formed from a rigid plastic slidably engagable with the lower end of the body 12 by means of interfitting tongues 14, 14' located on the lower end of the magazine body 12 and corresponding grooves 22, 22' in base 20. The magazine body 12 is formed from a single piece of steel or other like metal welded along a vertical weld line 13 in the center of the back wall of the magazine body 12. Base 20 is securely attached to the body 12 by retaining plate 24, which is secured to base 12 using screw 26. When secured in place, retaining plate 24 holds magazine body 12 in a fixed position relative to base 20. As illustrated in FIG. 2, rigid plastic base 12 extends downwardly from the handle 32 of pistol 30 when the magazine 10 is engaged in the well 34 of the pistol 30. The extended length of magazine 10 allows the magazine 10 to hold nine cartridges instead of the standard seven cartridges.
Additionally, in competition or sport shooting it may be advantageous for a shooter to rapidly eject a spent magazine and replace it with a full magazine. In this case it is common for shooters to allow the empty magazine to drop to the ground after being ejected from the well to facilitate the rapid reloading of the firearm. A rigid plastic base, such as that employed in the extended capacity magazine of FIG. 1, is susceptible to cracking or other damage upon impact with a hard surface, as would occur when the magazine is ejected from the firearm onto the ground. This may require the shooter to incur the expense of purchasing a new magazine. It is therefore also desirable to provide an extended capacity magazine which is resistant to damage when ejected from the well and allowed to drop onto a hard surface.
It is known that existing cartridge magazines are prone to jamming or otherwise failing to smoothly feed the cartridges through the magazine body into the firing chamber of the firearm. This tendency is primarily attributable to two features of existing cartridge magazines. First, as illustrated in FIG. 3A, the follower body 28 of most prior art magazines has been designed having a geometry and dimensions which allow the follower body to rotate or pivot clockwise and/or counter-clockwise relative to an end wall of the magazine body 12. FIG. 3B illustrates the aspect of the follower body (in an exaggerated depiction) being able to move side-to-side within the magazine body. It has been discovered that permitting the follower body 28 to pivot or rotate as little as two or three degrees within the magazine body may inhibit the smooth feeding of cartridges through the magazine and result in cartridge jamming. Second, as illustrated in FIG. 3B, it is traditional to weld cartridge magazines along a vertical weld line 13 in the center of the rear wall of the magazine body. Because cartridges are typically canted at some angle with respect to the horizontal, only the top portion of the rim of each cartridge makes contact with the back wall of the magazine body. Further, because the cartridges are centered within the magazine body, the rims contact the magazine body directly in the center of the back wall. Although the weld line 13 is typically sanded and polished, some surface imperfections may remain along the weld line. The rims of the cartridges may catch on these surface imperfections, which may cause the cartridges to jam or otherwise fail to feed smoothly into the firing chamber, as illustrated in FIG. 3A. It is therefore also particularly desirable to provide a cartridge magazine which consistently feeds cartridges to the firing chamber without jamming.